Bluetooth Low Energy (BLE) relates to Bluetooth wireless radio technology. It has been designed for low-power and low latency applications for wireless devices within short range. Today, BLE applications can be found from healthcare, fitness, security, smart energy, industrial automation and home entertainment. However, BLE is not limited only those, but increasingly more new application utilizing BLE technology are designed.
The difference between BLE and classic Bluetooth is that the BLE devices consume remarkably less power for communication than classic Bluetooth devices. In addition, the BLE is able to start the data transmission much quicker than the classic Bluetooth. This makes it possible to have BLE devices constantly on and to communicate intermittently with other devices.
In BLE technology, one or more so called slave devices can be connected to a master device. To let the master know about the slave devices before connection, the slave devices (or at that point “advertisers”) periodically, at pseudo-random intervals, pass advertisement packets which the master device (also known as scanner device, i.e. “scanner”) is scanning. Depending on the type of advertisement packet sent by an advertiser device, the scanner device may respond to the received advertisement packet by requesting a connection with the advertiser device, or may respond by requesting further information from the advertiser device. Beacons are a particular type of BLE advertiser device that transmit advertisement packets with a unique identifier to nearby portable electronic devices such as smart phones. An application on a portable electronic device may respond to information within an advertisement packet received from a beacon by performing an action, such as approximating the location of the portable device. After an advertiser device and scanner device become connected as master and slave, the master device may request bonding with the slave device. This means that the devices exchange long term keys or other encryption info to be stored for future connections. In another case, the master device may request pairing with the slave device, in which case the connection may be encrypted only for the duration of the current connection, during which short term keys are exchanged between the master device and slave device.
Restricting access to a wireless device for bonding or pairing purposes is usually accomplished by initial password authentication. In some cases, a password code is visibly printed onto an outside surface of the wireless device to be accessed. In such a case, a user desiring initial access to that wireless device needs to have visual access to the wireless device in order to see the printed password code on the device. The user may then input that visible code into another (accessing) device to allow the connection process. Other ways to restrict access to a wireless device for bonding or pairing purposes is to require a user to press a button or touch a display on the wireless device to be accessed, or to use another channel to transfer information to the wireless being accessed. However, such authentication technologies add cost & size to the wireless device. Yet another way of restricting access to a wireless device employs received signal strength (RSSI)-based filtering in an attempt to ensure that an accessing device has close proximity to the accessed device. However, RSSI is not always an accurate measure of device proximity since strong radio signals may sometimes be received from wireless devices that are outside the desired threshold distance range for allowing authentication.